Fuel injection apparatus for internal combustion engines

ABSTRACT

A fuel injector for use with an internal combustion engine comprising a body through which extends a passageway for fuel, the delivery of which is controlled by a valve member slidably mounted in a tubular guide in the passageway between the closed position to which it is urged by a spring and fully opened position determined by a stop nut on the valve stem, a flow restrictor being provided in the passageway to control maximum delivery rate of fuel when the valve member is fully open.

[451 Feb. 12, 1974 United States Patent [191 2 Pagdin Dahl......

Dahl......

966 Cadiou....... Svoboda...... 970 Halvorsen.......................

Erdington, Birmingham, England Mar. 5 1973 Primary Exammer-Robert S. Ward, Jr.

App]. No.: 338,682

Attorney, Agent, or Firm-Spencer & Kaye [22] Filed:

[30] Foreign Application Priority Data Mar. 3, 1972 Great Bmam 9942/72 A fuel injector for use with an internal combustion en- U S Cl 239/453 239/456 239/462 gine comprising a body through which extends a passageway for fuel, the delivery of which is controlled by a valve member slidably mounted in a tubular guide in the passageway between the closed position to which it is urged by a spring and fully opened position determined by a stop nut on the valve stem, a flow restric- 21 B340 1459 9 a ,5 3 4 2MO25 58 B ,5 904 7500 6 15 72 v n 65 547 u, ,5 H59 MN m M 5 53 Tm 3 m h NR $2 W 5 M I.

9 cum 9 mi IF UN 55 tor being provided in the passageway to control maximum delivery rate of fuel when the valve member is fully open.

2,297,487 L'Orange............................ 239/453 5 Claims, 2 Drawing Figures Fair/ ut t FUEL INJECTION APPARATUS FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to fuel injectors for use with fuel injection apparatus for internal combustion engines, such apparatus being of the kind which includes metering means establishing delivery of fuel from the fuel injection apparatus to each of the injectors in a series of discrete quantities (herein called pulses).

The present invention is based upon appreciation of certain desiderata to which a fuel injector should conform to achieve optimum performance. These desiderata are:-

a. that the fuel injector should incorporate valve means for confining the delivery of fuel to desired periods (substantially coexistent with the pulses of fuel delivered from the fuel injection apparatus), the valve means being capable of being moved with a minimum of delay from a closed position to an open position, so as to supply the fuel during the limited period when the air inlet valve of the associated cylinder of the engine is open;

b. that the fuel should be delivered in the form of a curtain which is sufficiently thin to enable the fuel readily to be broken up into droplets in the moving air stream established in the engine inlet manifold;

c. the effective cross-sectional area of the opening through which the fuel is delivered should be large enough to enable the pressure developed by the fuel injection apparatus to deliver a volume of fuel in each pulse in the time available (normally less than the period during which the inlet valve of the engine is open);

d. that the dimensions of the curtain should be controlled accurately to ensure that the thickness of the curtain is as uniform as possible in different positions therein;

e. that vapourisation of fuel in the injector should be minimised under conditions when the engine is at rest in the hot condition, to avoid prolonged cranking of the engine before liquid fuel is again delivered during subsequent starting;

f. that the injector should be capable of being disassembled and reassembled readily and preferably without the use of special tools.

The object of the present invention is to provide a new or improved form of injector which conforms more nearly to at least the first three, and preferably all, of these desiderata than those commonly available at the present time.

SUMMARY or; THE INVENTION According to the present invention a fuel injector for an internal combustion engine comprises a body having a passageway extending therethrough between an inlet and an outlet, a valve seat in said body at said outlet, a valve member removably mounted relatively to said body between a closed position with respect to said valve seat and a fully open position in response to a pulse of pressure in fuel being supplied to said passageway, spring means for urging said valve member towards its closed position, stop means for urging said valve member towards its closed position, stop means cooperative with said valve member for determining said fully open position, flow restrictor means in said passageway imposing a limit upon the quantity of fuel which can be delivered during each pressure pulse as the repetition frequency of pulses increases with increasing engine speed.

As engine speed increases a limit is reached as to the rate of flow at which air can be aspired into the engine, and consequently if the volume of fuel delivered during each pulse is determined by the parameters of absolute pressure and temperature in the air inlet manifold, an over-rich mixture will result. The restrictor means tends to produce merging of successive pressure pulses incident at the valve means'and shortens the open time of the valve means in respect of each pulse, thereby starving the engine and maintaining properfuel-to-air ratio under these conditions.

It is preferred that the valve means comprises a valve head having an annular valve face which in the fully open position of the valve is spaced from the valve seat, the latter also being of annular form to produce an approximately conical curtain of fuel, the valve member having a stem cooperating with guide means in the body to maintain the cross-sectional dimensions of the interspace between the valve face and the valve seat substantially constant at all positions around the axis of the valve head.

Opening of the valve member is produced in response to thrust due to the pressure of fuel in the passageway acting over the piston area of the valve member, and the restrictor means preferably comprises a barrier element disposed in the passageway upstream of the valve member and having a control orifice of cross-sectional area less than the cross-sectional area presented between the valve face and the valve seat when the valve member is in its fully open position.'

A further feature of the invention is that the body of the injector may comprise an inner metal member incorporating the passageway aforesaid and an outer mounting bush embracing the body and formed of a material of low thermal conductivity, such bush being adapted to be fitted in an aperture in the inlet manifold of the engine with which the injector is required to be used.

Preferably also the injector comprises a filter element disposed in the passageway. Advantageously the filter element is situated in the'passageway at a position upstream of the restrictor means. The filter element may comprise a cup-shaped body of porous metallic material such as porous bronze.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described, by way of example, with reference to the accompanying drawing wherein:-

FIG. I is a view in diametral longitudinal crosssection of one embodiment of injector in accordance with the invention;

FIG. 2 is a fragmentary cross-sectional view on an enlarged scale.

DESCRIPTION OF THE PREFERRED EMBODIMENT ally tubular form and made of any suitable metal, such as mild steel, and an outer component 11 in the form of a bush having a flange 12 made of a non-metallic material of low thermal conductivity so as to be capable of acting as a heat insulator. One suitable material for this purpose is nylon which has a coefficient of thermal conductivity of 6 X 10" cal/sec/ cm /O /Cm. The heat insulation provided by the bush 11 reduces transmission of heat from the manifold to the body and prevents, or substantially reduces, the risk of vapourisation of liquid fuel resident in the body during idle periods when the engine, with which the injector is used, is hot and, of course, also during running.

The bush 11 is adapted in any suitable manner to be secured in an aperture in the manifold. It may be a sliding (plug-in) fit in an aperture in the manifold and retained by a thin steel clip or there maybe an external screw thread on the bush cooperating with the threaded aperture in the manifold.

The inner component 10 of the body is formed with an axially extending passageway 13 for the flow of fuel between an inlet 13a and outlet 13b.

At the upper end of this passageway is provided a connection fitting 14 to enable a fuel pipe to be connected to the injector. The fitting has a male screwthreaded portion 14a engagingin a female threaded portion 10a of component 10. A resilient sealing member such as an O-ring 14b provides a fluid-tight joint.

In the lower part of the component 10 a tubular guide 15 is fitted in the passageway terminating in an annular or ring-like valve seat 16 having a face 16a of frustoconical form and maintainedin fluid-tight relation with the component 10 by way of resilient sealing member such as an O-ring 17 contained in an annular cavity 18 in the component 10.

A valve member 19 is slidably mounted in the tubular guide 15 and has a head 20 having a frusto-conical or like valve face 20a cooperating with the valve seat 16a, and a stem 22 guided by the interior surface of the tubular guide 15.

At its upper end the stem 22 has screw-threaded portion 23a and carries an adjusting nut 23.

A coiled compression spring 24 acting between the nut 23 and a flange 15a at the lower end of the tubular guide 15 serves to urge the valve into its closed position as shown in the drawing, in which the valve face 200 is in contact with the face 16a of the valve seat 16.

The valve is moved to its open position by pressure of fuel in the passageway 13 acting on the piston area of the valve member, namely thearea presented by the stem 22 together with the area of the annular zone of the valve face 20a situated within the face 160 of valve seat 16 when the valve member is in its closed position.

1 Within the passageway 13, and upstream of the valve member, there is provided a filter means comprising a cup-shaped filter element 25 preferably of porous bronze having a flange 26whi ch is clamped between a restrictor means 27 and the male element 14a on the inlet fitting.

The restrictor means 27 comprises a barrier element or washer formed of impermeable material, such as a metal, and having a control orifice 29 through which fuel, filtered by the element 25, can pass into the lower part of the passageway. The control orifice would typically have a diameter between 0.5mm and 1.5mm.

During operation the fuel injection apparatus provides pressure pulses of fuel at the inlet 13a to the passageway 13. These are transmitted through the filter element 25 and control orifice 29 and are incident over the piston area of the valve member.

The strength of the compression spring 24 is such that the valve member opens when a predetermined pressure has been achieved (for example 50 lbs. per square inch) and remains open throughout the pulse, pressure remaining substantially constant within the passageway 13 at this time, until the trailing edge of the pressure pulse is reached, when the valve member closes as soon as the pressure falls below the predetermined value. I

During this operation the cross-sectional dimensions of the passageway between the valve face 20a and the face 16a of seat 16 are maintained substantially constant at all positions around the axis of the valve member, and, therefore, approximately conical curtain of fuel of uniform wall thickness is delivered from the outonset of a pressure pulse so far as the piston area of the valve member is concerned.

Consequently, when an engine is set to operate with a full throttle opening and near its limit of speed the rate of pressure rise permitted by the control orifice 29 does not allow the valve member to open for substantially the full duration of each pulse, as would be the case were the speed of the engine lower or were the throttle opening smaller (in which latter case the metering means would restrict the quantity of fuel delivered during each pulse). I

Thus should there be a tendency for the mixture to become over-rich through inability of the engine to aspire the necessary mass of air, the control orifice 29 produces automatically a reduction in the quantity of fuel and thereby enables the correct air-to-fuel ratio to be maintained.

I claim: 1. A fuel injector for use with an internal combustion engine comprising:-

a. a body having a passageway extending therethrough between an inlet and an outlet, b. a valve seat in said body at said outlet, 0. a valve member removably mounted relatively to said body between a closed position with respect to said valve seat and a fully open position in response to a pulse of pressure in fuel being supplied to said passageway, i

d. spring means for urging said valve member towards its closed position,

e. stop means cooperative with said valve member for determining said fully open position,

f. flow restrictor means in said passageway imposing a limit upon the quantity of fuel which can be delivered during each pressure pulse as the repetition frequency of pulses increases with increasing engine speed.

2. An injector according to claim 1 wherein:-

a. said valve member includesavalve head having an b. said barrier element has a control orifice of a annular valve face which in the fully open position cross-sectional area less than the cross-sectional of Said Valve member is spaced from Said Valve area of the aperture defined between said valve Seat seat and the valve face of the valve member when b. said valve seat is also of annular form for defining 5 the valve member is in i f ll open position in combination with said valve member an outlet aperture providing for delivery of an approximately conical curtain of fuel,

c. guide means are provided in said body for slidably receiving a stem on said valve member to guide the 10 latter and maintain the cross-sectional dimensions 4. An injector according to claim 1 wherein said body comprises:-

a. an inner metal member incorporating said passageay. b. an outer mounting bush embracing said inner of said outlet aperture defined between said valve metal member formed of l of low member face and said valve seat substantially conthermal conducuvny Sald bush bemg adapted to fit Stam at all positions around Said valve head in an aperture in an-inlet manifold of said engine. 3, A i j according to l i 2 h l5 5. An injector according to claim 1 further comprisa. said restrictor means comprises a barrier element g a filter element disposed in Said passageway at a P disposed in said passageway at a position upstream sition upstream of said restrictor means.

of said valve seat 

1. A fuel injector for use with an internal combustion engine comprising:a. a body having a passageway extending therethrough between an inlet and an outlet, b. a valve seat in said body at said outlet, c. a valve member removably mounted relatively to said body between a closed position with respect to said valve seat and a fully open position in response to a pulse of pressure in fuel being supplied to said passageway, d. spring means for urging said valve member towards its closed position, e. stop means cooperative with said valve member for determining said fully open position, f. flow restrictor means in said passageway imposing a limit upon the quantity of fuel which can be delivered during each pressure pulse as the repetition frequency of pulses increases with increasing engine speed.
 2. An injector according to claim 1 wherein:-a. said valve member includes a valve head having an annular valve face which in the fully open position of said valve member is spaced from said valve seat, b. said valve seat is also of annular form for defining in combination with said valve member an outlet aperture providing for delivery of an approximately conical curtain of fuel, c. guide means are provided in said body for slidably receiving a stem on said valve member to guide the latter and maintain the cross-sectional dimensions of said outlet aperture defined between said valve member face and said valve seat substantially constant at all positions around said valve head.
 3. An injector according to claim 2 wherein:-a. said restrictor means comprises a barrier element disposed in said passageway at a position upstream of said valve seat b. said barrier element has a control orifice of a cross-sectional area less than the cross-sectional area of the aperture defined between said valve seat and the valve face of the valve member when the valve member is in its fully open position.
 4. An injector according to claim 1 wherein said body comprises: -a. an inner metal member incorporating said passageway, b. an outer mounting bush embracing said inner metal member and formed of a material of low thermal conductivity, said bush being adapted to fit in an aperture in an inlet manifold of said engine.
 5. An injector according to claim 1 further comprising a filter element disposed in said passageway at a position upstream of said restrictor means. 